“We’ve determined that the existing separation distances between helicopter traffic operating on Route 4 and aircraft landing on Runway 33 are insufficient and pose an intolerable risk to aviation safety by increasing the chances of a mid-air collision at DCA,” NTSB Chair Jennifer Homendy said during a news conference.

Current airport flight safety practices create an "intolerable safety risk" that could be eliminated by changing allowed separation distances between helicopters and airplanes, federal officials say.

Federal investigators looking for the cause of the January collision between a passenger jet and an Army helicopter near Washington, D.C., that killed 67 people are recommending a ban on some helicopter flights.